Polishing pad and method for making the same

ABSTRACT

The present invention relates to a polishing pad and method for making the same. In the invention, a liquid-state polymer material is directly formed on the surface of a base material, and then the liquid-state polymer material is solidified to form a flat grinding layer. Whereby, the polishing pad has high unity and flatness. The grinding layer has attenuated structures and a plurality of holes, thus increasing the storage ability of polishing particles distributed in a polishing liquid. In addition, the polishing pad has high compression ratio, so the polishing pad can compactly contact a polishing workpiece, and will not scratch the surface of the polishing workpiece scratched. Therefore, the polishing effect and quality will be improved.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation-in-part of the pending U.S. Pat. application Ser. No. 12/208,520 filed on Sep. 11, 2008, all of which is hereby incorporated by reference in its entirety.

Although incorporated by reference in its entirety, no arguments or disclaimers made in the parent application apply to this CIP application. Any disclaimer that may have occurred during the prosecution of the above-referenced application(s) is hereby expressly rescinded. Consequently, the Patent Office is asked to review the new set of claims in view of the entire prior art of record and any search that the Office deems appropriate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a polishing pad and method for making the same, in particular, to a polishing pad with a grinding layer directly formed on the surface of a base material and a method for making the same.

2. Description of the Related Art

Generally speaking, a polishing process is performed on a rough surface through chemical mechanical polishing (CMP). In the polishing process, a slurry containing polishing particles is uniformly distributed on the surface of a polishing pad. After a polishing workpiece is pressed on the polishing pad, a repetitious and regular rubbing and polishing action is performed thereon. The polishing workpiece may be a semiconductor, a storage medium base material, an integrated circuit, an LCD flat panel glass, optical glass, or a photoelectric panel.

In the prior art, a polishing pad is made by means of multi-layer adhesion. For example, a grinding layer is adhered to a base material through a self-adhesive (referring to a multi-layer polishing pad disclosed in R.O.C. Patent Publication No. M269996), or a grinding layer made by adhesion of a plurality of thin layers is adhered to a base material through a self-adhesive (referring to a multi-layer polishing pad used for CMP disclosed in R.O.C. Patent Publication No. 200513348).

After the above conventional polishing pads are immersed in a slurry, as the grinding layer, the base material, and the self-adhesive used for adhering are made of different materials and have different compression ratios, stress is easily generated. Further, after immersion in the slurry for a long time, the adhesiveness of the self-adhesive is gradually reduced, thus resulting in unevenness of the surface of the polishing pad. In addition, during the polishing process, when the polishing machine applies a pressure to polish a polishing workpiece, protrusions on the surface of the polishing pad may cause serious abrasion of the grinding layer as well as scratches on the surface of the polishing workpiece.

Moreover, the conventional polishing pads are limited by the thickness of the grinding layer. If no long holes are formed for storing the slurry and chippings generated after polishing, the holes may be filled with the chippings generated after polishing and easily become smaller. As a result, the polishing effect is reduced, and the service life of the polishing pad is shortened.

Consequently, there is an existing need for a polishing pad and a method for making the same to solve the above-mentioned problems.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a polishing pad having a base material and a grinding layer. The base material is formed by covering a fiber layer with a polymer and has a surface. The grinding layer is bonded to the surface and has a plurality of holes.

The present invention is further directed to a method for making a polishing pad. The method includes: (a) providing a base material formed by covering a fiber layer with a polymer and having a surface; (b) forming a liquid-state polymer material on the surface; and (c) solidifying the liquid-state polymer material to form a grinding layer. The grinding layer is bonded to the surface and has a plurality of holes.

In the present invention, the liquid-state polymer material is directly formed on the surface of the base material, and is then solidified to form the flat grinding layer, which makes the polishing pad very even and flat. The grinding layer has attenuated structures and holes, which increases the ability to store the polishing particles distributed in a polishing liquid. In addition, the polishing pad has high compression ratio, so the polishing pad can compactly contact a polishing workpiece, and will not scratch the surface of the polishing workpiece. Therefore, the polishing effect and quality will be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a polishing pad of the present invention;

FIG. 2 is a schematic view of another aspect of a polishing pad according to the present invention; and

FIG. 3 is a flow chart of a method for making a polishing pad according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a polishing pad used in a chemical mechanical polishing (CMP) process for polishing or planarizing a polishing workpiece. The polishing workpiece includes, but is not limited to, a semiconductor, a storage medium base material, an integrated circuit, an LCD flat panel glass, optical glass, and a photoelectric panel.

FIG. 1 is a schematic view of a polishing pad of the present invention. The polishing pad 1 includes a base material 11 and a grinding layer 12. In this embodiment, the base material 11 is formed by covering a fiber layer 112 with a polymer 111, and has a surface 113. Preferably, the surface 113 is flattened. The fiber layer 112 is made of a cloth material (for example, a non-woven cloth). In this embodiment, the polymer 111 is continuous foam. In addition, the polymer 111 is selected from PU, PP, PET, or polymer resin. The material of the fiber layer 112 is selected from at least one of PP, PET, or nylon.

The grinding layer 12 is bonded to the surface 113 of the base material 11, and is disposed on the surface 113 of the base material 11. That is, the grinding layer 12 does not extend into the interior of the base material 11, so that the polishing pad 1 is a double layered structure. The grinding layer 12 has a plurality of holes 121 and a polishing surface 122. The holes 121 are columnar-like cells, and each of the columnar-like cells 121 is in a shape of column rather than in a shape of water drop. Preferably, the distribution thickness of the holes 121 is at least half of the total thickness of the grinding layer 12. That is, the holes 121 are distributed over a thickness that is at least one half of the overall thickness of the grinding layer 12. In this embodiment, the depth of some of the columnar-like cells 121 is greater than one half of the overall thickness of the grinding layer 12. The columnar-like cells 121 properly communicate with each other. In this embodiment, the holes 121 extend toward the polishing surface 122 of the grinding layer 12, and are substantially perpendicular to the polishing surface 122 of the grinding layer 12. Some of the holes 121 are completely disposed inside the grinding layer 12, that is, some of the holes 121 are embedded in the grinding layer 12, and completely enclosed by the grinding layer 12. Therefore, some of the holes 121 do not have opening on the polishing surface 122 of the grinding layer 12.

In this embodiment, the polishing pad 1 has a compression ratio of 5% to 50%, a recovery ratio greater than 80%, a thickness of 0.5 to 3.0 mm, and a density of 0.2 to 0.6 g/cm³.

Further, in other applications, some of the fibers 114 in the fiber layer 112 are exposed on the surface 113 of the base material 11, and are further covered by the grinding layer 12 (as shown in FIG. 2). Therefore, the grinding layer 12 is not only attached to the surface 113 of the base material 11, but also covers the fibers 114 of the fiber layer 112. Thus, the grinding layer 12 is bonded to the base material 11 more stably.

FIG. 3 is a flow chart of a method for making a polishing pad according to the present invention. As shown in FIGS. 2 and 3, first, in Step S21, a base material 11 is provided. The base material 11 is formed by covering a fiber layer 112 with a polymer 111, and has a surface 113. In this embodiment, the base material 11 is formed through the following steps. First, a fiber substrate is provided. Then, the fiber substrate is immersed in a polymer solution, so that the polymer solution covers the fiber substrate. Finally, the polymer solution is solidified to form the base material 11.

Next, in Step S22, a liquid-state polymer material is formed on the surface of the base material 11. In this embodiment, the liquid-state polymer material is formed on the surface 113 of the base material 11 by coating, but not limited to coating. Obviously, the liquid-state polymer material can be formed on the surface 113 of the base material 11 in other manners. In addition, the liquid-state polymer material is selected from at least one of PU, PP, PET, or polymer resin.

Afterwards, in Step S23, the liquid-state polymer material is solidified to form a grinding layer 12, so as to complete the polishing pad 1 of the present invention. The grinding layer 12 is bonded to the surface 113 of the base material 11 and has a plurality of holes 121. In this solidification step, the liquid-state polymer material can be solidified by natural drying or air drying.

It should be noted that, after the liquid-state polymer material is formed on the surface 113 of the base material 11 and then solidified to form a flat surface (the polishing surface 122), the flat surface (the polishing surface 122) is further immersed in and contacts a liquid-state polymer material in a coagulating basin, so as to form the holes 121 of the grinding layer 12 through single surface exchange. Thus, the grinding layer 12 grows into the attenuated structure. The grinding layer 12 is disposed on the surface 113 of the base material 11. That is, the grinding layer 12 does not extend into the interior of the base material 11, so that the polishing pad 1 is a double layered structure. The holes 121 are columnar-like cells, and each of the columnar-like cells 121 is in a shape of column rather than in a shape of water drop. Preferably, the holes 121 are distributed over a thickness that is at least one half of the overall thickness of the grinding layer 12. In this embodiment, the holes 121 extend toward the polishing surface 122 of the grinding layer 12, and are substantially perpendicular to the polishing surface 122 of the grinding layer 12. Some of the holes 121 are completely disposed inside the grinding layer 12, that is, some of the holes 121 are embedded in the grinding layer 12, and completely enclosed by the grinding layer 12. Therefore, some of the holes 121 do not have opening on the polishing surface 122 of the grinding layer 12.

In the present invention, the liquid-state polymer material is directly formed on the surface 113 of the base material 11, and is then solidified to form the flat grinding layer 12, which makes the polishing pad very even and flat. The grinding layer 12 has attenuated structures and the holes 121, which increases the ability to store the polishing particles distributed in a polishing liquid. In addition, the polishing pad 1 has high compression ratio, so the polishing pad 1 can compactly contact a polishing workpiece, and will not scratch the surface of the polishing workpiece. Therefore, the polishing effect and quality will be improved.

While the embodiments of the present invention have been illustrated and described, various modifications and improvements can be made by those skilled in the art. The embodiments of the present invention are to therefore described in an illustrative but not restrictive sense. It is intended that the present invention may not be limited to the particular forms as illustrated, and that all modifications that maintain the spirit and scope of the present invention are within the scope as defined in the appended claims. 

1. A polishing pad, comprising: a base material, formed by covering a fiber layer with a polymer, and having a surface; and a grinding layer, bonded to the surface, and having a plurality of holes, wherein each of the holes is in a shape of column, the holes are distributed over a thickness that is at least one half of the overall thickness of the grinding layer, the depth of some of the holes is greater than one half of the overall thickness of the grinding layer, and the holes communicate with each other, some of the holes are completely disposed inside the grinding layer.
 2. The polishing pad according to claim 1, wherein the fiber layer is made of a cloth material.
 3. The polishing pad according to claim 2, wherein the cloth material is a non-woven cloth.
 4. The polishing pad according to claim 1, wherein the material of the fiber layer is selected from PP, PET, or nylon.
 5. The polishing pad according to claim 1, wherein the polymer is continuous foam.
 6. The polishing pad according to claim 5, wherein the polymer is selected from PU, PP, PET, or polymer resin.
 7. The polishing pad according to claim 1, wherein the surface is flattened, and the grinding layer is made of one material selected from PU, PP, PET, or polymer resin.
 8. The polishing pad according to claim 1, wherein some fibers in the fiber layer are exposed on the surface, and are further covered by the grinding layer.
 9. The polishing pad according to claim 1, wherein the compression ratio of the polishing pad is 5% to 50%.
 10. The polishing pad according to claim 1, wherein the recovery ratio of the polishing pad is greater than 80%.
 11. The polishing pad according to claim 1, wherein a thickness of the polishing pad is 0.5 to 3.0 mm.
 12. The polishing pad according to claim 1, wherein the density of the polishing pad is 0.2 to 0.6 g/cm³.
 13. A method for making a polishing pad, comprising: (a) providing a base material, wherein the base material is formed by covering a fiber layer with a polymer and has a surface; (b) forming a liquid-state polymer material on the surface; and (c) solidifying the liquid-state polymer material to form a grinding layer, wherein the grinding layer is bonded to the surface and has a flat surface; and (d) immersing the flat surface of the grinding layer in a coagulating basin, so as to form a plurality of holes in the grinding layer through single surface exchange, wherein each of the holes is in a shape of column rather than in a shape of water drop, the holes are distributed over a thickness that is at least one half of the overall thickness of the grinding layer, the depth of some of the holes is greater than one half of the overall thickness of the grinding layer, the holes communicate with each other, and some of the holes are completely disposed inside the grinding layer.
 14. The making method according to claim 13, wherein Step (a) further comprises: (a1) providing a fiber substrate; (a2) immersing the fiber substrate in a polymer solution, so that the polymer solution covers the fiber substrate; and (a3) solidifying the polymer solution to form the base material.
 15. The making method according to claim 13, wherein in Step (b), the liquid-state polymer material is formed on the surface by coating.
 16. The making method according to claim 13, wherein in Step (c), to the liquid-state polymer material is solidified by natural drying.
 17. The making method according to claim 13, wherein in Step (c), the liquid-state polymer material is solidified by air drying. 